Field of the Invention
This disclosure relates generally to:                drying volatile hydrocarbon gases by condensation, and to recovering and/or recycling dried hydrocarbon gases; and to:        recovering and/or recycling reactive hydrocarbon gases by condensation.        
Description of Related Art
A de Laval nozzle, or convergent-divergent nozzle, is a tube that is pinched in the middle, and has an axisymmetric hourglass shape. De Laval nozzles are used to accelerate pressurized gases at low speed to a higher speed, more particularly a supersonic speed in the axial direction, by converting the heat energy of the flow into kinetic energy. Because of this, the nozzle is used in steam turbines, rocket engine nozzles, and supersonic jet engines.
Operation of a de Laval nozzle depends on changing properties in a gas as it accelerates from subsonic to supersonic speeds. The speed of a subsonic flow of gas will increase if the pipe carrying it narrows because the mass flow rate is constant. The gas flow through a de Laval nozzle is normally isentropic. At the “throat,” where the cross-sectional area is at its minimum and flow is choked, the gas velocity reaches Mach 1. As the nozzle cross-sectional area increases, the gas expands, and the gas velocity becomes supersonic. Under conditions of supersonic flow at constant, or nearly constant, entropy, the gas temperature decreases and the gas pressure decreases.
As the gas temperature decreases, gases within the stream may condense and form a liquid or solid phase. By inducing swirl in the gas flow, the condensed phase may be driven by centrifugal force to the wall of the nozzle, and recovered through an opening at the nozzle wall or in a flow pipe leading away from the nozzle. Such techniques have been used to remove water from methane streams, e.g., natural gas. The current application is directed to removing water from higher-boiling hydrocarbon streams, and/or effectively separating C2 to C4 hydrocarbons under supersonic conditions.
Such separations are illustrative of those that can be achieved by the various embodiments disclosed herein, and are not intended to be exhaustive or limiting of the possible advantages that can be realized. Thus, these and other embodiments will be apparent from the description herein or can be learned from practicing the various exemplary embodiments, both as embodied herein or as modified in view of any variation that may be apparent to those skilled in the art. Accordingly, the present invention is exemplified by, but not limited to, the methods, arrangements, combinations, and improvements herein shown and described.